Evolved machine type communication design for shared radio frequency spectrum operation

ABSTRACT

Aspects of the present disclosure provide techniques utilizing shared radio frequency spectrum (SRFS) for certain devices, such as machine type communication(s) (MTC) user equipments (UEs) and evolved or enhanced MTC (eMTC) UEs. An exemplary method, performed, for example, by a base station (BS), includes performing a channel clear assessment (CCA) for at least a portion of the SRFS including one or more narrowband regions, and communicating with at least one MTC UE, after performing the CCA, on at least one of the narrowband regions. A second exemplary method, performed, for example, by a MTC UE, generally includes receiving, from a BS, an assignment of resources in a narrowband region of the SRFS band for the MTC UE to use for communicating with the BS, and communicating with the BS on the narrowband region without performing a CCA for the narrowband region. A third exemplary method, performed, for example, by a MTC UE, generally includes performing a CCA for a narrowband region of the SRFS band and communicating with a BS on the narrowband region.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present Application for Patent claims priority to U.S. ProvisionalApplication No. 62/152,768, filed Apr. 24, 2015, which is assigned tothe assignee of the present application and hereby expresslyincorporated by reference herein in its entirety.

BACKGROUND

1. Field of the Disclosure

Certain aspects of the present disclosure generally relate to wirelesscommunications and, more particularly, to evolved or enhanced machinetype communication(s) (eMTC) operations in shared radio frequencyspectrum (SRFS).

2. Description of the Related Art

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, data, and so on. Thesesystems may be multiple-access systems capable of supportingcommunication with multiple users by sharing the available systemresources (e.g., bandwidth and transmit power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE)/LTE-Advanced systems andorthogonal frequency division multiple access (OFDMA) systems.

Generally, a wireless multiple-access communication system cansimultaneously support communication for multiple wireless terminals.Each terminal communicates with one or more base stations viatransmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the base stations to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the base stations. This communication linkmay be established via a single-input single-output, multiple-inputsingle-output or a multiple-input multiple-output (MIMO) system.

A wireless communication network may include a number of base stationsthat can support communication for a number of wireless devices.Wireless devices may include user equipments (UEs). Some UEs may beconsidered machine-type communication (MTC) UEs, which may includeremote devices, that may communicate with a base station, another remotedevice, or some other entity. Machine type communications (MTC) mayrefer to communication involving at least one remote device on at leastone end of the communication and may include forms of data communicationwhich involve one or more entities that do not necessarily need humaninteraction. MTC UEs may include UEs that are capable of MTCcommunications with MTC servers and/or other MTC devices through PublicLand Mobile Networks (PLMN), for example.

Shared radio frequency spectrum (SRFS) includes radio frequency spectrumthat is unlicensed, and thus usable by large number and variety ofdevices, including, for example, Wi-Fi devices operating according toversions of the IEEE 802.11 standard. Devices utilizing SRFS may performlisten before talk (LBT) operations. LBT is generally the operation ofreceiving for a short period of time on a frequency band and determiningthat no other device is transmitting on that frequency band beforetransmitting on that frequency band.

SUMMARY

Certain aspects of the present disclosure provide techniques andapparatus for utilizing shared radio frequency spectrum (SRFS) forcertain devices, such as machine type communication (MTC) UEs andevolved machine type communication (eMTC) UEs.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a base station (BS) using a shared radio frequencyspectrum (SRFS) band. The method generally includes performing a channelclear assessment (CCA) for at least a portion of the SRFS including oneor more narrowband regions, and communicating with at least one machinetype communications (MTC) user equipment (UE), after performing the CCA,on at least one of the narrowband regions.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a machine type communications (MTC) user equipment(UE) using a shared radio frequency spectrum (SRFS) band. The methodgenerally includes receiving, from a base station (BS), an assignment ofresources in a narrowband region of the SRFS band for the MTC UE to usefor communicating with the BS, and communicating with the BS on thenarrowband region without performing a clear channel assessment (CCA)for the narrowband region.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a machine type communications (MTC) user equipment(UE) using a shared radio frequency spectrum (SRFS) band. The methodgenerally includes performing a clear channel assessment (CCA) for anarrowband region of the SRFS band and communicating with a base station(BS) on the narrowband region.

Certain aspects of the present disclosure provide an apparatus forwireless communications using a shared radio frequency spectrum (SRFS)band. The apparatus generally includes at least one processor configuredto perform a channel clear assessment (CCA) for at least a portion ofthe SRFS including one or more narrowband regions and to communicatewith at least one machine type communications (MTC) user equipment (UE),after performing the CCA, on at least one of the narrowband regions. Theapparatus may further include a memory coupled to the at least oneprocessor.

Certain aspects of the present disclosure provide an apparatus forwireless communications using a shared radio frequency spectrum (SRFS)band. The apparatus generally includes at least one processor configuredto receive, from a base station (BS), an assignment of resources in anarrowband region of the SRFS band for the MTC UE to use forcommunicating with the BS and to communicate with the BS on thenarrowband region without performing a clear channel assessment (CCA)for the narrowband region. The apparatus may further include a memorycoupled to the at least one processor.

Certain aspects of the present disclosure provide an apparatus forwireless communications using a shared radio frequency spectrum (SRFS)band. The apparatus generally includes at least one processor configuredto perform a clear channel assessment (CCA) for a narrowband region ofthe SRFS band and to communicate with a base station (BS) on thenarrowband region. The apparatus may further include a memory coupled tothe at least one processor.

Certain aspects of the present disclosure provide an apparatus forwireless communications using a shared radio frequency spectrum (SRFS)band. The apparatus generally includes means for performing a channelclear assessment (CCA) for at least a portion of the SRFS including oneor more narrowband regions and means for communicating with at least onemachine type communications (MTC) user equipment (UE), after performingthe CCA, on at least one of the narrowband regions.

Certain aspects of the present disclosure provide an apparatus forwireless communications using a shared radio frequency spectrum (SRFS)band. The apparatus generally includes means for receiving, from a basestation (BS), an assignment of resources in a narrowband region of theSRFS band for the MTC UE to use for communicating with the BS and meansfor communicating with the BS on the narrowband region withoutperforming a clear channel assessment (CCA) for the narrowband region.

Certain aspects of the present disclosure provide an apparatus forwireless communications using a shared radio frequency spectrum (SRFS)band. The apparatus generally includes means for performing a clearchannel assessment (CCA) for a narrowband region of the SRFS band andmeans for communicating with a base station (BS) on the narrowbandregion.

Certain aspects of the present disclosure provide a computer-readablemedium storing computer executable code. The computer executable codegenerally includes code to perform a channel clear assessment (CCA) forat least a portion of the SRFS including one or more narrowband regionsand code to communicate with at least one machine type communications(MTC) user equipment (UE), after performing the CCA, on at least one ofthe narrowband regions.

Certain aspects of the present disclosure provide a computer-readablemedium storing computer executable code. The computer executable codegenerally includes code to receive, from a base station (BS), anassignment of resources in a narrowband region of the SRFS band for theMTC UE to use for communicating with the BS and code to communicate withthe BS on the narrowband region without performing a clear channelassessment (CCA) for the narrowband region.

Certain aspects of the present disclosure provide a computer-readablemedium storing computer executable code. The computer executable codegenerally includes code to perform a clear channel assessment (CCA) fora narrowband region of the SRFS band and code to communicate with a basestation (BS) on the narrowband region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram conceptually illustrating an example of awireless communication network, in accordance with certain aspects ofthe present disclosure.

FIG. 2 shows a block diagram conceptually illustrating an example of abase station in communication with a user equipment (UE) in a wirelesscommunications network, in accordance with certain aspects of thepresent disclosure.

FIG. 3 is a block diagram conceptually illustrating an example of aframe structure in a wireless communications network, in accordance withcertain aspects of the present disclosure.

FIG. 4 is a block diagram conceptually illustrating two exemplarysubframe formats with the normal cyclic prefix.

FIG. 5 illustrates an exemplary subframe configuration for eMTC, inaccordance with certain aspects of the present disclosure.

FIGS. 6A and 6B illustrate an example of MTC co-existence within awideband system, such as LTE, in accordance with certain aspects of thepresent disclosure.

FIG. 7 illustrates example operations for wireless communications by abase station (BS), in accordance with certain aspects of the presentdisclosure.

FIG. 8 illustrates example operations for wireless communications, by anMTC user equipment (UE), in accordance with certain aspects of thepresent disclosure.

FIG. 9 illustrates example operations for wireless communications, by anMTC user equipment (UE), in accordance with certain aspects of thepresent disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure provide techniques that may helpenable communication between a base station (BS) and machine typecommunication (MTC) based user equipments (UEs) using shared radiofrequency spectrum (SRFS). For example, the techniques may providetechniques for reserving a narrowband (e.g., a six physical resourceblock (PRB)) region for communications between a BS and an MTC UE.Techniques for performing clear channel assessment (CCA), a type of LBT,while communicating in a narrowband region of SRFS are also provided.

As used herein, a “narrowband region” may refer to a 1.08 MHz (e.g., 6resource blocks (RBs)) narrowband region of a larger system bandwidthand/or a smaller narrowband region (e.g., 180 kHz) of a wider systembandwidth. As used herein, LTE Release 13 (Rel-13) narrowband internetof things (NB-IOT) may refer to a 180 kHz narrowband region of a widersystem bandwidth.

As used herein, “MTC” may refer to machine type communication(s) orinternet of things, such as NB-IOT. MTC UE generally refers to a UE thatcommunicates via a radio network but is not regularly used fordelivering communications directly to a user, such as electric metersthat report electricity usage data to billing system computers. As usedherein, the term “MTC UE” may refer to an MTC UE that utilizes an entiresystem bandwidth (e.g., an LTE Release 12 (Rel-12) MTC UE), an MTC UEthat utilizes a 1.08 MHz narrowband region of a larger system bandwidth(e.g., an LTE Release 13 (Rel-13) enhanced or evolved MTC (eMTC) UE),and/or an MTC UE that utilizes a smaller narrowband region (e.g., 180kHz) of a wider system bandwidth (e.g., a Rel-13 NB-IOT MTC UE). Whileaspects of the present disclosure are described in terms of MTC UEs thatutilize a 1.08 MHz (e.g., 6 RBs) narrowband region of a larger systembandwidth for convenience, these descriptions are not limiting of thepresent disclosure. Aspects of the present disclosure may be utilizedwith MTC UEs that utilize an entire system bandwidth, MTC UEs thatutilize a 1.08 MHz narrowband region of a larger system bandwidth, andMTC UEs that utilize a smaller narrowband region (e.g., 180 kHz) of awider system bandwidth. MTC UEs include devices such as sensors,monitors, meters, location tags, security devices, robots/roboticdevices, drones, etc. To enhance coverage of certain devices, such asMTC UEs, “bundling” may be utilized in which certain transmissions aresent as a bundle of transmissions, for example, with the sameinformation transmitted over multiple subframes.

The techniques described herein may be used for various wirelesscommunication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asuniversal terrestrial radio access (UTRA), cdma2000, etc. UTRA includeswideband CDMA (WCDMA), time division synchronous CDMA (TD-SCDMA), andother variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network may implement a radio technology such asglobal system for mobile communications (GSM). An OFDMA network mayimplement a radio technology such as evolved UTRA (E-UTRA), ultra mobilebroadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Flash-OFDM®, etc. UTRA and E-UTRA are part of universal mobiletelecommunication system (UMTS). 3GPP Long Term Evolution (LTE) andLTE-Advanced (LTE-A), in both frequency division duplex (FDD) and timedivision duplex (TDD), are new releases of UMTS that use E-UTRA, whichemploys OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA,UMTS, LTE, LTE-A and GSM are described in documents from an organizationnamed “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB aredescribed in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). The techniques described herein may beused for the wireless networks and radio technologies mentioned above aswell as other wireless networks and radio technologies. For clarity,certain aspects of the techniques are described below forLTE/LTE-Advanced, and LTE/LTE-Advanced terminology is used in much ofthe description below. LTE and LTE-A are referred to generally as LTE.

FIG. 1 illustrates an example wireless communication network 100, inwhich aspects of the present disclosure may be practiced. For example,techniques presented herein may be used to help UEs and BSs shown inFIG. 1 communicate on a machine type physical downlink control channel(mPDCCH) using a narrowband (e.g., six-PRB) based search space.

The network 100 may be an LTE network or some other wireless network.Wireless network 100 may include a number of evolved Node Bs (eNBs) 110and other network entities. An eNB is an entity that communicates withuser equipments (UEs) and may also be referred to as a base station, aNode B, an access point, etc. Each eNB may provide communicationcoverage for a particular geographic area. In 3GPP, the term “cell” canrefer to a coverage area of an eNB and/or an eNB subsystem serving thiscoverage area, depending on the context in which the term is used.

An eNB may provide communication coverage for a macro cell, a pico cell,a femto cell, and/or other types of cell. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having association with the femto cell (e.g.,UEs in a closed subscriber group (CSG)). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a pico cell may be referred to asa pico eNB. An eNB for a femto cell may be referred to as a femto eNB ora home eNB (HeNB). In the example shown in FIG. 1, an eNB 110 a may be amacro eNB for a macro cell 102 a, an eNB 110 b may be a pico eNB for apico cell 102 b, and an eNB 110 c may be a femto eNB for a femto cell102 c. An eNB may support one or multiple (e.g., three) cells. The terms“eNB”, “base station” and “cell” may be used interchangeably herein.

Wireless network 100 may also include relay stations. A relay station isan entity that can receive a transmission of data from an upstreamstation (e.g., an eNB or a UE) and send a transmission of the data to adownstream station (e.g., a UE or an eNB). A relay station may also be aUE that can relay transmissions for other UEs. In the example shown inFIG. 1, a relay station 110 d may communicate with macro eNB 110 a and aUE 120 d in order to facilitate communication between eNB 110 a and UE120 d. A relay station may also be referred to as a relay eNB, a relaybase station, a relay, etc.

Wireless network 100 may be a heterogeneous network that includes eNBsof different types, e.g., macro eNBs, pico eNBs, femto eNBs, relay eNBs,etc. These different types of eNBs may have different transmit powerlevels, different coverage areas, and different impact on interferencein wireless network 100. For example, macro eNBs may have a hightransmit power level (e.g., 5 to 40 Watts) whereas pico eNBs, femtoeNBs, and relay eNBs may have lower transmit power levels (e.g., 0.1 to2 Watts).

A network controller 130 may couple to a set of eNBs and may providecoordination and control for these eNBs. Network controller 130 maycommunicate with the eNBs via a backhaul. The eNBs may also communicatewith one another, e.g., directly or indirectly via a wireless orwireline backhaul.

UEs 120 (e.g., 120 a, 120 b, 120 c) may be dispersed throughout wirelessnetwork 100, and each UE may be stationary or mobile. A UE may also bereferred to as an access terminal, a terminal, a mobile station, asubscriber unit, a station, etc. Some examples of UEs may includecellular phones (e.g., smart phones), personal digital assistants(PDAs), wireless modems, handheld devices, tablets, laptop computers,netbooks, smartbooks, ultrabooks, wearable devices (e.g., smart watches,smart bracelets, smart clothing, smart glasses, smart goggles, heads-updisplays), robots/robotic devices, drones, entertainment devices (e.g.,music players, gaming devices), cameras, navigation devices, vehiculardevices, medical devices, healthcare devices, etc. In FIG. 1, a solidline with double arrows indicates desired transmissions between a UE anda serving eNB, which is an eNB designated to serve the UE on thedownlink and/or uplink. A dashed line with double arrows indicatespotentially interfering transmissions between a UE and an eNB.

FIG. 2 shows a block diagram of a design of base station/eNB 110 and UE120, which may be one of the base stations/eNBs and one of the UEs inFIG. 1. Base station 110 may be equipped with T antennas 234 a through234 t, and UE 120 may be equipped with R antennas 252 a through 252 r,where in general T≧1 and R≧1.

At base station 110, a transmit processor 220 may receive data from adata source 212 for one or more UEs, select one or more modulation andcoding schemes (MCS) for each UE based on CQIs received from the UE,process (e.g., encode and modulate) the data for each UE based on theMCS(s) selected for the UE, and provide data symbols for all UEs.Transmit processor 220 may also process system information (e.g., forSRPI, etc.) and control information (e.g., CQI requests, grants, upperlayer signaling, etc.) and provide overhead symbols and control symbols.Processor 220 may also generate reference symbols for reference signals(e.g., the CRS) and synchronization signals (e.g., the PSS and SSS). Atransmit (TX) multiple-input multiple-output (MIMO) processor 230 mayperform spatial processing (e.g., precoding) on the data symbols, thecontrol symbols, the overhead symbols, and/or the reference symbols, ifapplicable, and may provide T output symbol streams to T modulators(MODs) 232 a through 232 t. Each modulator 232 may process a respectiveoutput symbol stream (e.g., for OFDM, etc.) to obtain an output samplestream. Each modulator 232 may further process (e.g., convert to analog,amplify, filter, and upconvert) the output sample stream to obtain adownlink signal. T downlink signals from modulators 232 a through 232 tmay be transmitted via T antennas 234 a through 234 t, respectively.

At UE 120, antennas 252 a through 252 r may receive the downlink signalsfrom base station 110 and/or other base stations and may providereceived signals to demodulators (DEMODs) 254 a through 254 r,respectively. Each demodulator 254 may condition (e.g., filter, amplify,downconvert, and digitize) its received signal to obtain input samples.Each demodulator 254 may further process the input samples (e.g., forOFDM, etc.) to obtain received symbols. A MIMO detector 256 may obtainreceived symbols from all R demodulators 254 a through 254 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 258 may process (e.g., demodulateand decode) the detected symbols, provide decoded data for UE 120 to adata sink 260, and provide decoded control information and systeminformation to a controller/processor 280. A channel processor maydetermine RSRP, RSSI, RSRQ, CQI, etc.

On the uplink, at UE 120, a transmit processor 264 may receive andprocess data from a data source 262 and control information (e.g., forreports comprising RSRP, RSSI, RSRQ, CQI, etc.) fromcontroller/processor 280. Processor 264 may also generate referencesymbols for one or more reference signals. The symbols from transmitprocessor 264 may be precoded by a TX MIMO processor 266 if applicable,further processed by modulators 254 a through 254 r (e.g., for SC-FDM,OFDM, etc.), and transmitted to base station 110. At base station 110,the uplink signals from UE 120 and other UEs may be received by antennas234, processed by demodulators 232, detected by a MIMO detector 236 ifapplicable, and further processed by a receive processor 238 to obtaindecoded data and control information sent by UE 120. Processor 238 mayprovide the decoded data to a data sink 239 and the decoded controlinformation to controller/processor 240. Base station 110 may includecommunication unit 244 and communicate to network controller 130 viacommunication unit 244. Network controller 130 may include communicationunit 294, controller/processor 290, and memory 292.

Controllers/processors 240 and 280 may direct the operation at basestation 110 and UE 120, respectively. For example, controller/processor240 and/or other controllers, processors and modules at base station 110may, for example, perform direct operations 700 shown in FIG. 7.Similarly, controller/processor 280 and/or other controllers, processorsand modules at UE 120 may, for example, perform or direct operations 800shown in FIG. 8 and operations 900 shown in FIG. 9. Memories 242 and 282may store data and program codes for base station 110 and UE 120,respectively. A scheduler 246 may schedule UEs for data transmission onthe downlink and/or uplink.

FIG. 3 shows an exemplary frame structure 300 for FDD in LTE. Thetransmission timeline for each of the downlink and uplink may bepartitioned into units of radio frames. Each radio frame may have apredetermined duration (e.g., 10 milliseconds (ms)) and may bepartitioned into 10 subframes with indices of 0 through 9. Each subframemay include two slots. Each radio frame may thus include 20 slots withindices of 0 through 19. Each slot may include L symbol periods, e.g.,seven symbol periods for a normal cyclic prefix (as shown in FIG. 3) orsix symbol periods for an extended cyclic prefix. The 2L symbol periodsin each subframe may be assigned indices of 0 through 2L−1.

In LTE, an eNB may transmit a primary synchronization signal (PSS) and asecondary synchronization signal (SSS) on the downlink in the center ofthe system bandwidth for each cell supported by the eNB. The PSS and SSSmay be transmitted in symbol periods 6 and 5, respectively, in subframes0 and 5 of each radio frame with the normal cyclic prefix, as shown inFIG. 3. The PSS and SSS may be used by UEs for cell search andacquisition. The eNB may transmit a cell-specific reference signal (CRS)across the system bandwidth for each cell supported by the eNB. The CRSmay be transmitted in certain symbol periods of each subframe and may beused by the UEs to perform channel estimation, channel qualitymeasurement, and/or other functions. The eNB may also transmit aphysical broadcast channel (PBCH) in symbol periods 0 to 3 in slot 1 ofcertain radio frames. The PBCH may carry some system information. TheeNB may transmit other system information such as system informationblocks (SIBs) on a physical downlink shared channel (PDSCH) in certainsubframes. The eNB may transmit control information/data on a physicaldownlink control channel (PDCCH) in the first B symbol periods of asubframe, where B may be configurable for each subframe. The eNB maytransmit traffic data and/or other data on the PDSCH in the remainingsymbol periods of each subframe.

FIG. 4 shows two exemplary subframe formats 410 and 420 with the normalcyclic prefix. The available time frequency resources may be partitionedinto resource blocks. Each resource block may cover 12 subcarriers inone slot and may include a number of resource elements. Each resourceelement may cover one subcarrier in one symbol period and may be used tosend one modulation symbol, which may be a real or complex value.

Subframe format 410 may be used for two antennas. A CRS may betransmitted from antennas 0 and 1 in symbol periods 0, 4, 7 and 11. Areference signal is a signal that is known a priori by a transmitter anda receiver and may also be referred to as pilot. A CRS is a referencesignal that is specific for a cell, e.g., generated based on a cellidentity (ID). In FIG. 4, for a given resource element with label Ra, amodulation symbol may be transmitted on that resource element fromantenna a, and no modulation symbols may be transmitted on that resourceelement from other antennas. Subframe format 420 may be used with fourantennas. A CRS may be transmitted from antennas 0 and 1 in symbolperiods 0, 4, 7 and 11 and from antennas 2 and 3 in symbol periods 1 and8. For both subframe formats 410 and 420, a CRS may be transmitted onevenly spaced subcarriers, which may be determined based on cell ID.CRSs may be transmitted on the same or different subcarriers, dependingon their cell IDs. For both subframe formats 410 and 420, resourceelements not used for the CRS may be used to transmit data (e.g.,traffic data, control data, and/or other data).

The PSS, SSS, CRS and PBCH in LTE are described in 3GPP TS 36.211,entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); PhysicalChannels and Modulation,” which is publicly available.

An interlace structure may be used for each of the downlink and uplinkfor FDD in LTE. For example, Q interlaces with indices of 0 through Q−1may be defined, where Q may be equal to 4, 6, 8, 10, or some othervalue. Each interlace may include subframes that are spaced apart by Qframes. In particular, interlace q may include subframes q, q+Q, q+2Q,etc., where q ε{0, . . . , Q−1}.

The wireless network may support hybrid automatic retransmission request(HARQ) for data transmission on the downlink and uplink. For HARQ, atransmitter (e.g., an eNB) may send one or more transmissions of apacket until the packet is decoded correctly by a receiver (e.g., a UE)or some other termination condition is encountered. For synchronousHARQ, all transmissions of the packet may be sent in subframes of asingle interlace. For asynchronous HARQ, each transmission of the packetmay be sent in any subframe.

A UE may be located within the coverage of multiple eNBs. One of theseeNBs may be selected to serve the UE. The serving eNB may be selectedbased on various criteria such as received signal strength, receivedsignal quality, pathloss, etc. Received signal quality may be quantifiedby a signal-to-noise-and-interference ratio (SINR), or a referencesignal received quality (RSRQ), or some other metric. The UE may operatein a dominant interference scenario in which the UE may observe highinterference from one or more interfering eNBs.

Example Control Channel Design For Machine Type Communications

As noted above, aspects of the present disclosure provide techniques forsignalling control channels to machine type communication (MTC) devicesthat may use a narrowband region of a larger system bandwidth. Such anarrowband region may be, for example, a Rel-13 eMTC narrowband with1.08 MHz (e.g., six RBs) of bandwidth or a Rel-13 NB-IOT narrowband with180 kHz (e.g., one RB) of bandwidth.

The focus of traditional LTE design (e.g., for legacy “non MTC” devices)is on the improvement of spectral efficiency, ubiquitous coverage, andenhanced quality of service (QoS) support. Current LTE system downlink(DL) and uplink (UL) link budgets are designed for coverage of high enddevices, such as state-of-the-art smartphones and tablets, which maysupport a relatively large DL and UL link budget.

However, it is desirable that low cost, low rate devices be supported aswell. For example, certain standards (e.g., LTE Release 12) haveintroduced a new type of UE (referred to as a category 0 UE) generallytargeting low cost designs or machine type communications. For machinetype communications (MTC), various requirements may be relaxed as only alimited amount of information may need to be exchanged. For example,maximum bandwidth may be reduced (relative to legacy UEs), a singlereceive radio frequency (RF) chain may be used, peak rate may be reduced(e.g., a maximum of 100 bits for a transport block size), transmit powermay be reduced, Rank 1 transmission may be used, and half duplexoperation may be performed.

In some cases, if half-duplex operation is performed, MTC UEs may have arelaxed switching time to transition from transmitting to receiving (orreceiving to transmitting). For example, the switching time may berelaxed from 20 μs for regular UEs to 1 ms for MTC UEs. Release 12 MTCUEs may still monitor downlink (DL) control channels in the same way asregular UEs, for example, monitoring for wideband control channels inthe first few symbols (e.g., PDCCH) as well as narrowband controlchannels occupying a relatively narrowband, but spanning a length of asubframe (e.g., ePDCCH).

Certain standards (e.g., LTE Release 13) may introduce support forvarious additional MTC enhancements, referred to herein as enhanced MTC(or eMTC). For example, eMTC may provide MTC UEs with coverageenhancements up to 15 dB, which may be achieved, for example, bytransmission time interval (TTI) bundling of various channels (e.g.,PDSCH, PUSCH, PRACH, and/or MPDCCH).

As illustrated in the subframe structure 500 of FIG. 5, eMTC UEs cansupport narrowband operation while operating in a wider system bandwidth(e.g., 1.4/3/5/10/15/20 MHz). In the example illustrated in FIG. 5, aconventional legacy control region 510 may span system bandwidth of afirst few symbols, while a narrowband region 530 of the system bandwidth(spanning a narrow portion of a data region 520) may be reserved for anMTC physical downlink control channel (referred to herein as an mPDCCH)and for an MTC physical downlink shared channel (referred to herein asan mPDSCH). In some cases, an MTC UE monitoring the narrowband regionmay operate at 1.4 MHz or 6 resource blocks (RBs) and may usedemodulation reference signals (DM-RS) for demodulation.

However, as noted above, eMTC UEs may be able to operate in a cell witha bandwidth larger than 6 RBs. Within this larger bandwidth, each eMTCUE may still operate (e.g., monitor/receive/transmit) while abiding by a6-physical resource block (PRB) constraint. In some cases, differenteMTC UEs may be served by different narrowband regions (e.g., with eachspanning 6-PRB blocks).

In Release 11, an enhanced physical downlink control channel (ePDCCH)was introduced. In contrast to the PDCCH which spans a first few symbolsin a subframe, the ePDCCH is frequency division multiplexing (FDM) basedand spans (symbols of) the entire subframe. Additionally, as compared tothe conventional PDCCH CRS support, the ePDCCH may only support DM-RS.

In some cases, the ePDCCH may be UE-specifically configured. Forexample, each UE in a network may be configured to monitor a differentset of resources for an ePDCCH directed to that UE. Additionally, theePDCCH supports two modes of operation: localized ePDCCH, in which asingle precoder is applied to each PRB, and distributed ePDCCH, in whichtwo precoders cycle through the allocated resources within each PRBpair.

The ePDCCH may be constructed based on enhanced resource element groups(eREG) and enhanced control channel elements (eCCE). Generally, an eREGis defined by excluding DM-RS REs, assuming a maximum amount of DM-RS(e.g., 24 DM-RS REs in subframes using normal cyclic prefix and 16 DM-RSREs in subframes using extended cyclic prefix), and including anynon-DM-RS REs (REs that do not carry DM-RS). Thus, in subframes usingnormal cyclic prefix, the number of eREGs available for the ePDCCH is144 (12 subcarriers×14 symbols−24 DM-RS=144 REs), and, for extendedcyclic prefix, the number of REs available for the ePDCCH is 128 (12subcarriers*12 symbols−16 DM-RS=128 REs).

In some cases, a PRB pair is divided into 16 eREGs, regardless ofsubframe type, cyclic prefix type, PRB pair index, subframe index, etc.Thus, in subframes using normal cyclic prefix, there are 9 REs per eREG,and there are 8 REs per eREG in subframes using extended cyclic prefix.In some cases the eREG to RE mapping may follow a cyclic/sequential andfrequency-first-time-second manner, which may be beneficial toequalizing the number of available REs per eREG. Additionally, due tothe presence of other signals, the number of available REs for theePDCCH may not be fixed and can be different for different eREGs in aPRB pair.

As mentioned above, MTC and/or eMTC operation may be supported in thewireless communication network (e.g., in coexistence with LTE or someother RAT). FIGS. 6A and 6B, for example, illustrate an example of howMTC UEs in MTC operation may co-exist within a wideband system, such asLTE.

As illustrated in the example frame structure of FIG. 6A, subframes 610associated with MTC and/or eMTC operation may be time divisionmultiplexed (TDM) with regular subframes 620 associated with LTE (orsome other RAT).

Additionally or alternatively, as illustrated in the example framestructure of FIG. 6B, one or more narrowbands 650 used by MTC UEs in MTCmay be frequency division multiplexed (FDM) within the wider bandwidth660 supported by LTE. Multiple narrowband regions, with each narrowbandregion spanning a bandwidth that is no greater than a total of 6 RBs,may be supported for MTC and/or eMTC operation. In some cases, each MTCUE in MTC operation may operate within one narrowband region (e.g., at1.4 MHz or 6 RBs) at a time. However, MTC UEs in MTC operation, at anygiven time, may re-tune to other narrowband regions in the wider systembandwidth. In some examples, multiple MTC UEs may be served by the samenarrowband region. In other examples, multiple MTC UEs may be served bydifferent narrowband regions (e.g., with each narrowband region spanning6 RBs, or as mentioned above, a smaller number of RBs). In yet otherexamples, different combinations of MTC UEs may be served by one or moresame narrowband regions and/or one or more different narrowband regions.

The MTC UEs may operate (e.g., monitor/receive/transmit) within thenarrowband regions for various different operations. For example, asshown in FIG. 5B, a first narrowband region (e.g., spanning no more than6 RBs of the wideband data) of a subframe may be monitored by one ormore MTC UEs for either a PSS, SSS, PBCH, MTC signaling, or pagingtransmission from a BS in the wireless communication network. As alsoshown in FIG. 6B, a second narrowband region (e.g., also spanning nomore than 6 RBs of the wideband data) of a subframe may be used by MTCUEs to transmit a RACH or data previously configured in signalingreceived from a BS. In some cases, the second narrowband region may beutilized by the same MTC UEs that utilized the first narrowband region(e.g., the MTC UEs may have re-tuned to the second narrowband region totransmit after monitoring in the first narrowband region). In some cases(although not shown), the second narrowband region may be utilized bydifferent MTC UEs than the MTC UEs that utilized the first narrowbandregion.

Although the examples described herein assume a narrowband of 6 RBs,those skilled in the art will recognize that the techniques presentedherein may also be applied to different sizes of narrowband regions(e.g., 1 RB, etc.).

Example Machine Type Communications Operations Utilizing Shared RadioFrequency Spectrum

As noted above, devices operating in SRFS perform LBT. An MTC UE may notbe capable of simultaneously receiving over multiple narrowband regionsof an SRFS band. Such an MTC UE should detect a transmission thatoccupies a wideband (e.g., a 20 MHz wide band) region of an SRFS bandwhile receiving from one narrowband region of the wideband region. Thequantity of energy in the narrowband region is less than the totalenergy of the transmission, which is spread over the entire widebandregion. According to aspects of the present disclosure, techniques foran MTC UE to perform energy detection over a narrowband region of anSRFS band as part of a CCA are provided.

As mentioned previously, MTC devices may transmit and receive bundledtransmissions for coverage enhancement and other reasons. Previouslyused techniques of LBT (e.g., IEEE 802.11 CCAs) may not receive for along enough period of time to determine the frequency band is not goingto be used by another device for the entire length of a bundledtransmission. According to aspects of the present disclosure, techniquesfor a BS or UE performing MTC operations to perform CCAs for longerperiods of time to accommodate the durations of bundled transmissionsare provided.

According to aspects of the present disclosure, a BS (e.g., an eNB)acting as a controller of a cell supporting MTC UEs may perform a CCA orenhanced CCA (eCCA) over an SRFS band, and then transmit a Wi-Fi (e.g.,IEEE 802.11ax) preamble reserving the SRFS band for a period of timeequal to the sum of the time for the BS to transmit assignments oftransmission resources to one or more UEs and the time for the UEs tofollow the assignments (e.g., by transmitting or receiving per theassignments). The assignments may be conveyed via one or more PDCCHsand/or ePDCCHs, which may be bundled. Bundling (e.g., of transmissionsby the BS and transmissions by a UE) may be taken into account when theBS computes the period of time to reserve the SRFS band. The assignmentsmay be for the one or more MTC UEs to transmit or receive bundled and/ornon-bundled transmissions on narrowband regions of the SRFS band. TheMTC UEs may follow the one or more assignments without performing a CCA,because the Wi-Fi preamble transmitted by the BS reserved the SRFS bandfor the duration of the operations by the MTC UEs.

According to aspects of the present disclosure, the preamble transmittedby the BS may be a wideband (e.g., a 20 MHz wide frequency band)preamble. The wideband preamble may be detectable by both MTC UEs andnon-MTC UEs. The wideband preamble may be decodable by devices that canreceive a wideband signal (e.g., non-MTC UEs and BSs) and may reserve awideband region of the SRFS band for a period of time.

According to aspects of the present disclosure, the BS may transmit anarrowband preamble over a narrowband region of the SRFS band subsequentto transmitting a wideband preamble. The wideband preamble may bedecodable by devices that can receive a wideband signal (e.g., non-MTCUEs and BSs) and reserve a wideband region of the SRFS band for a periodof time. The narrowband preamble may be decodable by both devices thatcan receive a wideband signal and devices that cannot (e.g., MTC UEs).The narrowband preamble may reserve the narrowband region of the SRFSband for a period of time. Devices decoding either the wideband preambleor the narrowband preamble may refrain from transmitting over thereserved regions (either wideband or narrowband) for the periods of timeindicated by the preambles.

According to aspects of the present disclosure, a device (e.g., a BS,non-MTC UE, or MTC UE) may perform a CCA prior to transmitting a bundledtransmission on a narrowband region of an SRFS band and may compute aduration for the CCA based on a duration of the bundled transmission.The duration of the bundled transmission may be computed as a number oftransmission time intervals (TTIs) used for transmitting the bundledtransmission. The computed duration for the CCA may be only a fraction(e.g., 1/20) of the duration of the bundled transmission. For example, aBS may determine to transmit a bundled PDCCH over eight TTIs (e.g.,milliseconds) over a narrowband region of an SRFS band. In the example,the BS may compute the duration of a CCA to perform before startingtransmission of the bundled PDCCH as 8/20 of a TTI.

According to aspects of the present disclosure, a BS may transmit anindication of downlink transmissions over a narrowband region of an SRFSband prior to transmitting the downlink transmissions. That is, a BS maytransmit an indication over a narrowband region of a downlinktransmission to be transmitted over the narrowband region. The BS maytransmit the indication prior to performing a CCA for the indicateddownlink transmission. The indication may be, for example, an Msequence, a Chu sequence, or a downlink channel usage beacon signal(D-CUBS). A UE receiving the indication may cause a receiver of the UEto remain powered on and active for a duration exceeding a computedduration of a CCA to be performed by the BS. The UE may begin searchingfor the indicated DL signal at the end of the computed duration of theCCA. If the UE begins receiving a signal from the BS before the end ofthe duration, then the UE may continue to have the receiver powered onand active at least until the UE has received the DL transmission. Forexample, a UE may be operating in a coverage enhancement regime whereintransmissions from a serving BS of the UE are bundled over four TTIs. Inthe example, the serving BS may transmit a Chu sequence in a narrowbandregion of an SRFS band to indicate that the serving BS is going totransmit a DL signal to the UE. Still in the example, the UE decodes theChu sequence and calculates that a CCA performed by the BS will have aduration of 4/20 of a TTI. Still in the example, the UE determines toleave the receiver of the UE activated and to begin searching for a DLsignal from the BS 4/20 of a TTI after receiving the Chu sequence. Theindication may be, for example, a narrowband PCFICH, transmitted in thenarrowband which the intended UE monitors. The narrowband PCFICH signalcan further indicate downlink and uplink channel split, PLMNinformation, and/or other information.

According to aspects of the present disclosure, a BS may provide anindication of one or more TTIs to be used by a UE for transmitting arandom access channel (RACH) signal over a narrowband region of an SRFSband to the BS. A UE receiving the indication may determine to delaytransmitting a RACH signal to the BS over the narrowband region untilthe indicated TTIs.

According to aspects of the present disclosure, a UE may transmitchannel state indicator (CSI) feedback to a BS over a narrowband regionof an SRFS band. For aperiodic CSI feedback to a BS, the BS may triggerthe UE to provide aperiodic CSI feedback regarding the narrowband regionby requesting the CSI feedback in a grant transmitted to the UE. The BSmay reserve a wideband region including the narrowband region or onlythe narrowband region by transmitting a preamble, as described above.The UE may transmit the aperiodic CSI feedback on the narrowband regionwithout performing a CCA according to the grant received from the BS.For periodic CSI feedback, a BS may indicate a periodic opportunitywindow for a UE to transmit periodic CSI feedback on the narrowbandregion of the SRFS band. A UE may perform a CCA on the narrowband regionof the SRFS band prior to transmitting a periodic CSI feedback report tothe BS over the narrowband region.

According to aspects of the present disclosure, a BS (e.g., an eNB)acting as a controller of a cell supporting MTC UEs may perform a CCA orenhanced CCA (eCCA) over an SRFS band before transmitting to an MTC UEon a narrowband region of the SRFS band.

According to aspects of the present disclosure, an MTC UE may perform aCCA or eCCA on a narrowband region of the SRFS band before transmittingon the narrowband region of the SRFS band. A UE performing a CCA or eCCAon a narrowband region of an SRFS band may compute a threshold energylevel to be used in the CCA or eCCA, based on the size of the narrowbandregion and the size of a wideband region including the narrowbandregion. For example, if a UE is performing a CCA for a 1.08 MHz (e.g., 6RBs) narrowband region included in a 20 MHz (e.g., 110 RBs) widebandregion, then the UE may compute a threshold energy level for the CCAthat differs from a threshold energy level for a 20 MHz channel. In theexample, the UE may determine (e.g., by looking up in a table) that athreshold energy level of −62 dBm is used for a 20 MHz channel. Still inthe example, the UE may compute a threshold energy level for the CCA byusing the equation:

E _(CCA,NB) =E _(CCA,WB)−10 log₁₀ (WB/NB)  (1),

where E_(CCA,NB) is the threshold energy level for the narrowband CCA,

E_(CCA,WB) is the threshold energy level for a wideband CCA,

WB is the bandwidth of the wideband region, and

NB is the bandwidth of the narrowband region.

Still in the example, the UE may compute a threshold energy level forthe CCA of −75 dBm=−62 dBm−10 log₁₀ (20 MHz/1.08 MHz)

FIG. 7 illustrates example operations 700 for wireless communication bya base station (BS) using a shared radio frequency spectrum (SRFS) band,in accordance with certain aspects of the present disclosure describedabove. Operations 700 may be performed by a BS such as eNB 110 a shownin FIG. 1.

Operations 700 begin at 702, by performing a channel clear assessment(CCA) for at least a portion of the SRFS including one or morenarrowband regions. At 704, the operation continues by the BScommunicating with at least one machine type communications (MTC) userequipment (UE), after performing the CCA, on at least one of thenarrowband regions.

FIG. 8 illustrates example operations 800 for wireless communication bya machine type communications (MTC) user equipment (UE) using a sharedradio frequency spectrum (SRFS) band, in accordance with certain aspectsof the present disclosure described above. Operations 800 may beperformed by an MTC UE, such as UE 120 d shown in FIG. 1.

Operations 800 begin at 802, by the MTC UE receiving, from a basestation (BS), an assignment of resources in a narrowband region of theSRFS band for the MTC UE to use for communicating with the BS. At 804,the operation continues by the MTC UE communicating with the BS on thenarrowband region without performing a clear channel assessment (CCA)for the narrowband region.

FIG. 9 illustrates example operations 900 for wireless communication bya machine type communications (MTC) user equipment (UE) using a sharedradio frequency spectrum (SRFS) band, in accordance with certain aspectsof the present disclosure described above. Operations 900 may beperformed by an MTC UE, such as UE 120 d shown in FIG. 1.

Operations 900 begin at 902, by the MTC UE performing a clear channelassessment (CCA) for a narrowband region of the SRFS band. At 904, theoperation continues by the MTC UE communicating with a base station (BS)on the narrowband region.

In current (e.g., Release 12) LTE wireless communication protocols, a BS(e.g., eNB 110 a shown in FIG. 1) may transmit discovery referencesignals (DRS). DRS may include the previously mentioned PSS, SSS, CRS,and CSI-RS. The discovery reference signals may permit UEs served inneighboring cells to measure strength of signals (e.g., DRS), whichmeasurements the UEs may use in determining whether to reselect to acell served by the BS. A UE may be configured (e.g., by the UE's servingBS) with a bandwidth in which the UE measures DRS. For example, a UE maybe configured to measure DRS in a bandwidth of a neighboring cell todetermine if the UE should reselect to the neighboring cell. Theconfigured bandwidth for a UE may be 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15MHz, or 20 MHz.

According to aspects of the present disclosure, a BS may configurenarrowband DRS and transmit the narrowband DRS in one or more narrowbandregions of a wider system bandwidth. The narrowband DRS may betransmitted in the same frequency bands or different frequency bands asnormal (non-narrowband) DRS. The narrowband DRS may be use differentperiodicities and/or subframe offsets as normal DRS. For example andwith reference to FIG. 3, a BS may transmit normal PSS and normal SSS insymbols 6 and 5, respectively, of subframes 0 and 5 of every frame.Still in the example, the BS may configure and transmit narrowband PSSand narrowband SSS in symbols 9 and 8, respectively, of subframes 2 and7 of every frame. Still in the example and with reference to FIG. 5, thenormal PSS and normal SSS may be transmitted in the center 6 RBs of awider system bandwidth, while the narrowband PSS and narrowband SSS maybe transmitted in the narrowband region 530.

According to aspects of the present disclosure, a UE (e.g., an MTC UE)may be configured (e.g., by a serving BS of the UE) to search for and/ormeasure narrowband DRS in a narrowband region of a wider systembandwidth. The narrowband region may be, for example, a Rel-13 eMTCnarrowband with 1.08 MHz (e.g., six RBs) of bandwidth or a Rel-13 NB-IOTnarrowband with 180 kHz (e.g., one RB) of bandwidth. The UE may measurenarrowband DRS and report the measurements to a serving BS. For exampleand with reference to FIG. 5, an MTC UE may be configured to measurenarrowband CRS in the narrowband region 530 and report the measurementsto a serving BS of the UE.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: a, b, c,a-b, a-c, b-c, and a-b-c.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Softwareshall be construed broadly to mean instructions, data, code, or anycombination thereof, whether referred to as software, firmware,middleware, code, microcode, hardware description language, machinelanguage, or otherwise. Generally, where there are operationsillustrated in Figures, those operations may be performed by anysuitable corresponding means-plus-function components.

For example, means for performing may include one or more controllers orprocessors, such as the receive processor 258 and/or thecontroller/processor 280 of the user terminal 120 illustrated in FIG. 2and/or the transmit processor 220 and/or the controller/processor 240 ofthe base station 110 illustrated in FIG. 2. Means for receiving and/ormeans for communicating may comprise, e.g., the receive processor 258and/or an antenna(s) 252 of the user terminal 120 illustrated in FIG. 2,the transmit processor 220 and/or an antenna(s) 234 of the eNB 110illustrated in FIG. 2, etc. Means for transmitting and/or means forsending may comprise, e.g., the transmit processor 220 and/or anantenna(s) 234 of the eNB illustrated in FIG. 2. Means for determiningmay comprise, e.g., the controller/processor 280 and memory 282 of theuser terminal 120 illustrated in FIG. 2 and/or the controller processor240 and memory 242 of the base station 110 illustrated in FIG. 2.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or combinations thereof

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as hardware,software, or combinations thereof. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination thereof. A softwaremodule may reside in RAM memory, flash memory, ROM memory, EPROM memory,EEPROM memory, phase change memory, registers, hard disk, a removabledisk, a CD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, or combinations thereof. Ifimplemented in software, the functions may be stored on or transmittedover as one or more instructions or code on a computer-readable medium.Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage media may be anyavailable media that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation, suchcomputer-readable media can comprise RAM, ROM, EEPROM, CD/DVD or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method for wireless communications by a basestation (BS) using a shared radio frequency spectrum (SRFS) band,comprising: performing a channel clear assessment (CCA) for at least aportion of the SRFS including one or more narrowband regions; andcommunicating with at least one machine type communications (MTC) userequipment (UE), after performing the CCA, on at least one of thenarrowband regions.
 2. The method of claim 1, further comprisingtransmitting a preamble to reserve the at least one or more narrowbandregions.
 3. The method of claim 2, wherein the preamble comprises awideband preamble transmitted on a wideband region including a pluralityof the narrowband regions.
 4. The method of claim 3, wherein thewideband preamble is detectable by both MTC UEs and non-MTC UEs.
 5. Themethod of claim 3, further comprising transmitting at least onenarrowband preamble after transmitting the wideband preamble.
 6. Themethod of claim 2, further comprising transmitting an assignment ofresources in the one or more narrowband regions for the UE to use forcommunicating with the BS.
 7. The method of claim 1, wherein performingthe CCA comprises performing the CCA over a wideband region including aplurality of the narrowband regions.
 8. The method of claim 1, wherein:communicating with the at least one MTC UE comprises sending downlinktransmissions to the at least one MTC UE, the downlink transmissionssent as bundled transmissions over a plurality of transmission timeintervals (TTIs); and performing the CCA comprises performing the CCAover a window having a duration corresponding to only a fraction of theplurality of TTIs.
 9. The method of claim 1, wherein: communicating withthe at least one MTC UE comprises sending downlink transmissions to theat least one MTC UE; and the method further comprises transmitting anindication, in at least one narrowband region, of the downlinktransmissions prior to transmitting the downlink transmissions.
 10. Themethod of claim 9, wherein transmitting the indication comprisestransmitting at least one of an M sequence, a Chu sequence, or adownlink channel usage beacon signal (D-CUBS).
 11. The method of claim1, wherein: communicating with the at least one MTC UE comprisesreceiving a random access channel (RACH) transmission from the UE; andthe method further comprises providing, to the at least one MTC UE, anindication of transmission time intervals (TTIs) for transmitting theRACH.
 12. The method of claim 1, wherein: communicating with the atleast one MTC UE comprises receiving channel state indicator (CSI)feedback from the at least one MTC UE.
 13. The method of claim 1,further comprising: transmitting at least one discovery reference signal(DRS) on at least one of the narrowband regions.
 14. The method of claim13, further comprising: sending, to the at least one MTC UE, aconfiguration that configures the at least one MTC UE to receive atleast one discovery reference signal (DRS) on at least one of thenarrowband regions.
 15. A method for wireless communications by amachine type communications (MTC) user equipment (UE) using a sharedradio frequency spectrum (SRFS) band, comprising: receiving, from a basestation (BS), an assignment of resources in a narrowband region of theSRFS band for the MTC UE to use for communicating with the BS; andcommunicating with the BS on the narrowband region without performing aclear channel assessment (CCA) for the narrowband region.
 16. The methodof claim 15, wherein: communicating with the BS comprises transmittinguplink transmissions to the BS.
 17. The method of claim 15, wherein:communicating with the BS comprises receiving downlink transmissionsfrom the BS; and the method further comprises receiving an indication,in the narrowband region, of the downlink transmissions prior toreceiving the downlink transmissions.
 18. The method of claim 17,wherein the indication comprises at least one of an M sequence, a Chusequence, or a downlink channel usage beacon signal (D-CUBS).
 19. Themethod of claim 15, wherein: communicating with the BS comprisestransmitting channel state indicator (CSI) feedback to the BS.
 20. Themethod of claim 15, further comprising: receiving at least one discoveryreference signal (DRS) on at least one of the narrowband region oranother narrowband region of the SRFS band.
 21. The method of claim 20,further comprising: receiving a configuration from the BS, wherein theconfiguration configures the MTC UE to receive at least one discoveryreference signal (DRS) on at least one of the narrowband region oranother narrowband region of the SRFS band.
 22. A method for wirelesscommunications by a machine type communications (MTC) user equipment(UE) using a shared radio frequency spectrum (SRFS) band, comprising:performing a clear channel assessment (CCA) for a narrowband region ofthe SRFS band; and communicating with a base station (BS) on thenarrowband region.
 23. The method of claim 22, further comprising:determining a threshold energy level for the CCA based on a bandwidth ofthe narrowband region and a bandwidth of the SRFS band, whereinperforming the CCA comprises performing the CCA using the thresholdenergy level.
 24. The method of claim 22, further comprising receivingan assignment of resources in the narrowband region for the MTC UE touse for communicating with the BS.
 25. The method of claim 22, wherein:communicating with the BS comprises transmitting uplink transmissions tothe BS, the uplink transmissions sent as bundled transmissions over aplurality of transmission time intervals (TTIs); and performing the CCAcomprises performing the CCA over a window having a durationcorresponding to only a fraction of the plurality of TTIs.
 26. Themethod of claim 22, wherein: communicating with the BS comprisesreceiving downlink transmissions from the BS; and the method furthercomprises receiving an indication, in the narrowband region, of thedownlink transmissions prior to receiving the downlink transmissions.27. The method of claim 26, wherein the indication comprises at leastone of an M sequence, a Chu sequence, or a downlink channel usage beaconsignal (D-CUBS).
 28. The method of claim 22, wherein: communicating withthe BS comprises transmitting a random access channel (RACH)transmission; and the method further comprises obtaining, from the BS,an indication of transmission time intervals (TTIs) for transmitting theRACH.
 29. The method of claim 22, further comprising: receiving at leastone discovery reference signal (DRS) on at least one of the narrowbandregion or another narrowband region of the SRFS band.
 30. The method ofclaim 29, further comprising: receiving a configuration from the BS,wherein the configuration configures the MTC UE to receive at least onediscovery reference signal (DRS) on at least one of the narrowbandregion or another narrowband region of the SRFS band.